nt to attract attention to my experiments. You boys
have a wireless telegraph outfit on your Wondership?"

Jack nodded. He was curious, as was Tom, to know the Professor's plan.
They did not have long to wait.

"I wish you would get the machine ready to install a radio-telephone
outfit in its place. In that way I can gauge the limits of my
invention without attracting undue attention, as everybody in this
vicinity has seen you in flight and would imagine that you were merely
taking a trip through the air."

"But can you get out an apparatus light enough for us to take up?"
asked Jack.

"I am working on that now," said Mr. Chadwick. "I'll have it ready in
a week."

"We'll be ready for you," promised Jack.

CHAPTER VII.

THE GREAT TEST.

A week later to the day on a sunshiny, windless morning, the
Wondership was run out of its shed, glistening with new paint and with
every bit of bright work burnished till it shone and sparkled like
newly-minted silver. Amidships on the craft, the general construction
of which is familiar to readers of foregoing volumes of this series,
was a square metal box with small wires leading to long copper wires
stretched from end to end of the Wondership's body.

These long copper wires were to form the aerials by which the messages
from Mr. Chadwick's workshop were to be caught. The smaller wires
underneath were connected with the metal work of the engine. These
wires formed a "ground" similar to the kind employed in aerial
wireless telegraphy.

The details of the Wondership having been fully described in the Boy
Inventors' Flying Ship, we shall not enter here into any but a brief
and general description of the craft. The Wondership, then, was a
combination of dirigible balloon, automobile and boat. Her motive
power was furnished by engines driven by an explosive volatile gas
which was also used when occasion arose to inflate the bag of the
balloon feature of her design. The gas was generated in the lower part
of the craft's semi-cylindrical metal body.

On land two big aerial propellers, geared to the engine, drove the
Wondership swiftly along on four solid-tired wheels. When it was
desired to take to the air the balloon bag, which was neatly folded on
a framework supported by upright stanchions above the body of the car,
was inflated by turning on a valve connecting with the gas tanks in
the base of the body.

When the Wondership was intended to navigate the water she